Crosby.] 46 [October 2, 
points one-third of its volume, and, in the States of Barcelona and 
Cumana, composing the highest summits. With this exception, the 
littoral cordillera of the Spanish Main, as far west as Caraccas at 
least, is composed of the same rocks as on Trinidad, and the struc- 
ture is similar. There is little room to doubt that Trinidad, south of 
the Northern Mountains, is an isolated portion of the plain above 
described, which, probably in consequence of the greater disturbance 
which the rocks have experienced, is somewhat more elevated than 
the adjacent main. 
In short, the region between the littoral cordillera of the Spanish 
Main and Trinidad, and the crystalline rocks to the south of the 
Orinoco and in Guiana, is a natural basin, which, since middle Sec- 
ondary time, or possibly from a still earlier epoch, has been gradually 
silting up; and the process is not yet complete. The Gulf of Paria 
has an area of about twenty-five hundred square miles. It is a shal- 
low body of water, the greatest depth, except in the immediate 
vicinity of the Dragon’s Mouth, not exceeding twenty fathoms, with 
an average of less than ten fathoms. I have searched in vain for 
proof that this is an excavated basin. The land is certainly gaining, 
not wasting, along the western and south-western shores of the gulf; 
and such appears to be the case on the east side, except at a few 
salient points. Evidence is not wholly wanting, especially along the 
north side of the gulf, that it has resulted from a local subsidence ; 
but Iam more inclined to the view hinted at above, that it is a por- 
tion of the great basin of the Orinoco which has never been filled 
up. But, whatever the origin of the gulf, there can be no doubt 
that existing forces are rapidly obliterating it. Vast quantities of 
sediment are discharged into it by the Orinoco, Caroni, and other 
streams, and the delta of the first named river is steadily encroach- 
ing on the waters of the gulf. The annexation of Trinidad to the 
Continent by this means appears to be only a question of time. In 
fact, if the present conditions are maintained, the, geologically speak- 
ing, near future will witness considerable additions of terra firma to 
the north-east coast of South America. The southern half of the 
Orinoco delta will advance northward until it meets the southern 
coast of Trinidad and closes the Serpent’s Mouth. The intervening 
water is now for the most part quite shallow, and the greatest depth 
is scarcely thirty fathoms. The action of the sea on the Trinidad 
coast, it is true, tends to widen the strait; but at the same time, the 
detritus thus formed, being deposited in the strait, serves to make it 
